Created on 01.21
Understanding BS EN 12326: Why A1-W1-T1-S1 Classification is the Gold Standard for Your Roof
Natural slate is often heralded as the "100-year roof," but its longevity depends entirely on its geological composition and adherence to international standards78. At Red Tree Slate, our products are fully compliant with BS EN 12326, achieving the highest possible A1-W1-T1-S1 classification59. But what do these ratings mean for your building? The 'W1' rating signifies extremely low water absorption (less than 0.4%), making the slate naturally resistant to frost damage and moisture-related decay910.
The 'T1' rating ensures high resistance to thermal cycles, meaning the tiles won't warp or crack under extreme temperature fluctuations, while the 'S1' classification guarantees the slate is free from reactive mineral impurities like pyrites911. Some lower-quality slates contain pyrites that cause unsightly rust spots and structural weakening over time11. Our low-calcium slate is acid-resistant and chemically inert, making it an ideal roofing solution for harsh environments, including coastal areas and regions prone to acid rain1213. By demanding BS EN 12326 compliant materials, you ensure that your investment will stand the test of time, lasting for generations without the need for frequent maintenance914.